Are "L" lenses immune to condensation?

2 days ago I bought my first "L" lens; the 100-400mm L. Love it! I have heard that L lenses are waterproof and weather sealed. I ask because, normal lenses are affected by condensation when going from the cold outdoors to indoors. I also had a lense steam up with condensation at the Biodome. I crossed over from a dry cool section into the hot and humid Amazon section. My lens was foggy for a good 15 minutes.

Since L lenses are sealed, would they be immune to condensation in these situations?